Having seen wikis grow in multiple online communities this isn't really the case. The wiki begins to contain a lot of solid baseline information which is useful to everyone, but discussion about specific subjects is still very much alive. In the world of boating, there is an awful lot of indisputable, factual baseline information, but also a lot of boat-specific and troubleshooting questions which can continue to spur high quality discussion. The signal-to-noise ratio is already pretty bad in many places (for example, I was reading an older thread about HVO fuel the other day which contained more posts about propellers than it did about the topic subject, which would be fine if it were in its own topic; but going off topic is extremely common here).
I know I don't have many posts here but have been reading the forum extensively for some time and have used it as a knowledgebase to search for lots of things, so I believe a wiki would be amazing for organizing pertinent information in that way.